The original -ms macros were included with AT&T
troff as well as the man macros. While the man
package is intended for brief documents that can be read on-line as well
as printed, the ms macros are suitable for longer documents that
are meant to be printed rather than read on-line.
The ms macro package included with
groff is a complete,
bottom-up re-implementation. Several macros (specific to AT&T
or Berkeley) are not included, while several new commands are.
See Differences from AT&T ms, for more information.